AUTHOR=Zhou Tengsheng , Xu Wen , Hirani Arvind H. , Liu Zheng , Tuan Pham Anh , Ayele Belay T. , Daayf Fouad , McVetty Peter B. E. , Duncan Robert W. , Li Genyi 

TITLE=Transcriptional Insight Into Brassica napus Resistance Genes LepR3 and Rlm2-Mediated Defense Response Against the Leptosphaeria maculans Infection

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.00823

DOI=10.3389/fpls.2019.00823

ISSN=1664-462X

ABSTRACT=<p>The phytopathogenic fungus <italic>Leptosphaeria maculans</italic> causes the blackleg disease on <italic>Brassica napus</italic>, resulting in severe loss of rapeseed production. Breeding of resistant cultivars containing race-specific resistance genes is provably effective to combat this disease. While two allelic resistance genes <italic>LepR3</italic> and <italic>Rlm2</italic> recognizing <italic>L. maculans</italic> avirulence genes <italic>AvrLm1</italic> and <italic>AvrLm2</italic> at plant apoplastic space have been cloned in <italic>B. napus</italic>, the downstream gene expression network underlying the resistance remains elusive. In this study, transgenic lines expressing <italic>LepR3</italic> and <italic>Rlm2</italic> were created in the susceptible “Westar” cultivar and inoculated with <italic>L. maculans</italic> isolates containing different sets of <italic>AvrLm1</italic> and <italic>AvrLm2</italic> for comparative transcriptomic analysis. Through grouping the RNA-seq data based on different levels of defense response, we find <italic>LepR3</italic> and <italic>Rlm2</italic> orchestrate a hierarchically regulated gene expression network, consisting of induced ABA acting independently of the disease reaction, activation of signal transduction pathways with gradually increasing intensity from compatible to incompatible interaction, and specifically induced enzymatic and chemical actions contributing to hypersensitive response with recognition of <italic>AvrLm1</italic> and <italic>AvrLm2</italic>. This study provides an unconventional investigation into <italic>LepR3</italic> and <italic>Rlm2</italic>-mediated plant defense machinery and adds novel insight into the interaction between surface-localized receptor-like proteins (RLPs) and apoplastic fungal pathogens.</p>